title: Zinc causes acute impairment of glutathione metabolism followed by coordinated antioxidant defenses amplification in gills of brown mussels Perna perna.
abstract: Zinc demonstrates protective and antioxidant properties at physiological levels, although these characteristics are not attributed at moderate or high concentrations. Zinc toxicity has been related to a number of factors, including interference with antioxidant defenses. In particular, the inhibition of glutathione reductase (GR) has been suggested as a possible mechanism for acute zinc toxicity in bivalves. The present work investigates the biochemical effects of a non-lethal zinc concentration on antioxidant-related parameters in gills of brown mussels Perna perna exposed for 21 days to 2.6 μM zinc chloride. After 2 days of exposure, zinc caused impairment of the antioxidant system, decreasing GR activity and glutathione levels. An increase in antioxidant defenses became evident at 7 and 21 days of exposure, as an increase in superoxide dismutase and glutathione peroxidase activity along with restoration of glutathione levels and GR activity. After 7 and 21 days, an increase in cellular peroxides and lipid peroxidation end products were also detected, which are indicative of oxidative damage. Changes in GR activity contrasts with protein immunoblotting data, suggesting that zinc produces a long lasting inhibition of GR. Contrary to the general trend in antioxidants, levels of peroxiredoxin 6 decreased after 21 days of exposure. The data presented here support the hypothesis that zinc can impair thiol homeostasis, causes an increase in lipid peroxidation and inhibits GR, imposing a pro-oxidant status, which seems to trigger homeostatic mechanisms leading to a subsequent increase on antioxidant-related defenses.
authors.affiliation: Department of Biochemistry, Biological Sciences Centre, Federal University of Santa Catarina, 88040-900 Florianópolis, Santa Catarina, Brazil.
authors.forename: Rafael
authors.initials: R
authors.lastname: Trevisan
authors.forename: Samira
authors.initials: S
authors.lastname: Flesch
authors.forename: Jacó Joaquim
authors.initials: JJ
authors.lastname: Mattos
authors.forename: Márcio Raimundo
authors.initials: MR
authors.lastname: Milani
authors.forename: Afonso Celso Dias
authors.initials: AC
authors.lastname: Bainy
authors.forename: Alcir Luiz
authors.initials: AL
authors.lastname: Dafre
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D049872:Bivalvia / Q000187:drug effects* / Q000378:metabolism; D002712:Chlorides / Q000009:adverse effects*; D005880:Gills / Q000187:drug effects* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D005979:Glutathione Peroxidase / Q000378:metabolism; D005980:Glutathione Reductase / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D000075322:Heavy Metal Poisoning; D015227:Lipid Peroxidation / Q000187:drug effects; D019216:Metals, Heavy / Q000009:adverse effects; D049883:Perna / Q000187:drug effects* / Q000378:metabolism; D054465:Peroxiredoxin VI / Q000378:metabolism; D011041:Poisoning; D013482:Superoxide Dismutase / Q000378:metabolism; D017967:Zinc Compounds / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D002712:Chlorides; D019216:Metals, Heavy; D017967:Zinc Compounds; C016837:zinc chloride; D054465:Peroxiredoxin VI; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; D005980:Glutathione Reductase; D005982:Glutathione Transferase; D005978:Glutathione
keywords: Bivalves; Glutathione reductase; Metal; Oxidative stress; Peroxiredoxin; Thiol